The present invention is directed to a method for characterizing a plurality of organic or inorganic materials, and more particularly to a characterization method that uses a modular, electrically-driven sensor array in a selected standardized integrated electronic platform to characterize a plurality of materials simultaneously and rapidly.
Companies are turning to combinatorial materials science techniques for developing new compounds or materials (including formulations, materials having different processing histories, or mixtures of compounds) having novel physical and chemical properties. Combinatorial materials science refers generally to methods and apparatuses for creating a collection of chemically diverse compounds or materials and to methods and apparatuses for rapidly testing or screening such compounds or materials for desired performance characteristics and/or properties. The collections of chemical compounds or materials are commonly called xe2x80x9clibrariesxe2x80x9d. See U.S. Pat. No. 5,776,359, herein incorporated by reference, for a general discussion of combinatorial methodologies.
A virtually infinite number of useful materials or compounds can be prepared by combining different elements of the Periodic Table of Elements in varying ratios, by creating compounds with different arrangements of elements, and by creating materials comprising mixtures of compounds or formulations with differing processing histories. Discovery of useful materials for a particular application may require preparation or characterization of many candidate materials or compounds. Preparing and screening a large number of candidates increases the probability of useful discoveries. Thus, any system that can analyze and characterize the properties of combinatorially prepared library members quickly and accurately is highly desirable.
Many conventional measurement systems comprise a distinct specialized machine for characterizing a particular material property, so that testing of a candidate material can use many machines and be cumbersome and time-consuming. Also, most known materials characterization devices measure only one material sample at a time, severely limiting the number of samples that can be characterized per unit time.
Optical screening methods and devices have been preferred for many combinatorial chemistry and combinatorial materials science applications because they are non-contact and non-destructive. See for example WO 98/15805, incorporated herein by reference. For example, luminescence may be screened optically. When monitoring chemical reactions, for example, thermal imaging with an infrared camera can detect heat released during relatively fast exothermic reactions. See WO 98/15813, incorporated herein by reference. Although optical methods are particularly useful for characterizing materials or properties in certain circumstances, many materials characterization techniques are difficult or impossible to perform using optical methods. Therefore, there is still a need for a more direct materials characterization method that involves more intimate contact between the material samples and the sensing apparatus.
Conventional sensors that generate electrical data corresponding to material properties are typically designed as individual, discrete units, each sensor having its own packaging and wiring connections. Many materials characterization sensors are designed to be used individually in or with a machine that characterizes one sample at a time. Linking a plurality of these individual sensors in an array format, assuming that it is physically possible, would be expensive and often creates overly complicated wiring schemes with minimal gains in operating efficiency for the overall sensing system.
One structure using multiple material samples is a microfabricated array containing xe2x80x9cmicrohotplatesxe2x80x9d. The microhotplates act as miniature heating plates for supporting and selectively heating material samples placed thereon. U.S. Pat. No. 5,356,756 to Cavicchi et al and U.S. Pat. No. 5,345,213 to Semancik et al. as well the article entitled xe2x80x9cKinetically Controlled Chemical Sensing Using Micromachined Structures,xe2x80x9d by Semancik and Cavicchi, (Accounts of Chemical Research, Vol. 31, No. 5, 1998), all illustrate the microhotplate concept and are incorporated herein by reference. Although arrays containing microhotplates are known, they have been used primarily to create varied processing conditions for preparing materials. A need still exists for an array-based sensor system that can actually characterize material properties.
It is therefore an object of the invention to provide a materials characterization system that can measure properties of many material samples quickly, and in some embodiments simultaneously.
It is also an object of the invention to construct a materials characterization system having a modular structure that can be connected to a flexible electronic platform to allow many different material properties to be measured with minimal modification of the apparatus.
This invention provides an apparatus (or system) and method for testing materials in an array format using sensors that contact the materials being tested. Accordingly, the present invention is directed to an electronically-driven sensor array system for rapid characterization of multiple materials. A plurality of sensors are disposed on a substrate to form a sensor array. Properties that can be measured include thermal, electrical and mechanical properties of samples. Regardless of the property being measured or the specific apparatus, the materials characterization system of the invention includes a multiple sensors carrying multiple samples, means for routing signals to and from the sensors, electronic test circuitry, and a computer or processor to receive and interpret data from the sensors. In a preferred embodiment, a modular system is constructed including a single sensor array format, and signal routing equipment compatible with this format which can be used with multiple sensor types and multiple electronic test equipment types, permitting maximum flexibility of the system while preserving the general advantages of sensor array-based characterization. Alternatively, some or all of the different parts of the system may be integrated together into a single physical component of the system.
The sensors can be operated in serial or parallel fashion. A wide range of electronically driven sensors may be employed, which those of skill in the art will appreciate provide the opportunity to design an apparatus or method for specific applications or property measurements. The environment in which the measurement is made by the sensor can be controlled.
This invention allows for rapid screening of combinatorial libraries or large numbers of samples prepared by other means. This invention allows for property measurements that cannot be done optically. However, optical measurements may be made in conjunction with the sensor based electronic measurements of this invention. One potentially important feature is the speed of the property measurements made with this invention. Two independent reasons for this speed are that one can measure samples in parallel or with smaller sample sizes than with conventional measurement techniques. Moreover, automated sample handling, array preparation and/or sensor operation allows for a completely automated rapid property measurement system in accord with this invention.